diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..89de354
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,17 @@
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
diff --git a/action.yml b/action.yml
index 5333385..12522e1 100644
--- a/action.yml
+++ b/action.yml
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MIT
 name: 'Setup Forgejo'
 author: 'Forgejo authors'
 description: |
diff --git a/dependencies.sh b/dependencies.sh
index dfad405..3a9d606 100755
--- a/dependencies.sh
+++ b/dependencies.sh
@@ -1,4 +1,5 @@
 #!/bin/bash
+# SPDX-License-Identifier: MIT
 
 set -x
 
diff --git a/forgejo-runner.sh b/forgejo-runner.sh
index e041e69..0862e8c 100755
--- a/forgejo-runner.sh
+++ b/forgejo-runner.sh
@@ -1,4 +1,5 @@
 #!/bin/bash
+# SPDX-License-Identifier: MIT
 
 set -ex
 
diff --git a/forgejo-test-helper.sh b/forgejo-test-helper.sh
index 4a4b5cd..a9aa07a 100755
--- a/forgejo-test-helper.sh
+++ b/forgejo-test-helper.sh
@@ -1,4 +1,5 @@
 #!/bin/bash
+# SPDX-License-Identifier: MIT
 
 set -ex
 
diff --git a/forgejo.sh b/forgejo.sh
index e7bee3d..aa579e2 100755
--- a/forgejo.sh
+++ b/forgejo.sh
@@ -1,4 +1,5 @@
 #!/bin/bash
+# SPDX-License-Identifier: MIT
 
 set -ex
 
diff --git a/testdata/sanity-checks/.forgejo/workflows/test.yml b/testdata/sanity-checks/.forgejo/workflows/test.yml
index e8ab33e..bc8e798 100644
--- a/testdata/sanity-checks/.forgejo/workflows/test.yml
+++ b/testdata/sanity-checks/.forgejo/workflows/test.yml
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: MIT
 name: Setup Forgejo
 run-name: ${{ github.actor }} is setting up Forgejo
 on: [push]